The feeding behavior of fish consists of two phases: (1) an appetitive phase which includes an orienting response and a food search response, and (2) a consummatory phase which includes a snapping/biting response, masticating, and a swallowing response. The discovery of an agent that stimulates the biting response of fish would be of value for increasing food intake, not only to sport and commercial fishermen, but also to commercial fish pond owners.
In most fish, including members of the ictalurid family, such as channel catfish (Ictalurus punctatus), the chemical stimuli in the environment are detected by both their olfactory and gustatory receptors. Neurophysiological studies have shown that both the olfactory and the gustatory receptors of most fish, including iotalurid catfish, are sensitive to amino acids, such as those found in the natural substances on which fish feed (e.g., tissues of worms, mollusks, crustaceans, insects, amphibians, and teleosts).
Much work has been done in associating various amino acids with both gustatory and olfactory receptors in fish, particularly ictalurid catfish. See for example: "High Sensitivity of Catfish Taste Receptors to Amino Acids", by John Caprio, Comparative Biochemical Physiology, 1975, Vol. 52A, pp 247-251; "High Sensitivity and Specificity of Olfactory and Gustatory Receptors of Catfish to Amino Acids", by John Caprio, Chemoreception in Fishes, Elsevier Scientific Publishing Co., Amsterdam, 1982, Chapter 7, pp 109-1241; "An Electrophysiological Investigation of the Oro-Pharyngeal (IX-X) Taste System in the Channel Catfish, Ictalurus punctatus", by J. S. Kanwal and J. Caprio, Journal of Comparative Physiology, vol.150, 1983, pp 345-357; and "Receptor Sites For Amino Acids in the Facial Taste System of the Channel Catfish", by S. Wegert and J. Caprio, Journal of Comparative Physiology A, vol. 168, 1991, pp 201-211. While much work has been reported in the above articles, as well as others not listed above, with regard to the sensitivity of various gustatory and olfactory receptors to the amino acids, all of this work was from electrophysiological studies--not behavioral studies. That is, while experiments can be conducted to show that various receptors of a fish are sensitive to a particular agent, they cannot predict the behavior which will be associated with that particular agent. For example, it has been observed that a particular amino acid may either attract or repel fish, or even cause no behavior response, depending upon other past or present stimulations to the fish.
Even in those cases where fish have been attracted by the presence of certain compounds, the attraction has not been consistently followed by a increase in the feeding activity of the fish. Also, while a gustatory receptor may be equally sensitive to one stimulus which is sweet in taste, and another which is bitter or salty in taste, the behavior of the animal can be the opposite for each stimulus. In fact, of the three amino acids of the present invention for releasing the snapping/biting response, one, at least to humans, is very bitter (L-arginine) and another is sweet (L-alanine). Consequently, the fact that a particular agent can trigger an electrophysiological response in a receptor of a fish, it does not predict the corresponding behavior the fish will have to that agent.
In commercial catfish pond farming, it is desirable to utilize techniques which encourage pond catfish to feed on the food placed in the pond in order to obtain faster growth for the production of a higher quality fish fillet, as well as more efficient utilization of the food supplied to the pond. Another problem in commercial pond catfish farming results when the fish are placed under stress. This can occur during their movement into the pond from another location or environment, and also in disease. When in a state of stress, the fish often have a tendency not to eat. This can result in the loss of a substantial number of fish before they adapt to their new environment. Thus, it is important that the fish feed as soon as possible on the food supplied to them by the pond farmer.
While various attempts have been made to encourage fish to snap and take a particular food, or lure, there still exits a substantial need in the art for improved methods and chemical agents for accomplishing this.